This invention relates generally to a miniature motor, and more particularly to a miniature motor in which a flexible photo-setting resin is applied to brush arms to prevent brushes from unwantedly vibrating during rotation of a commutator.
In recent years, miniature motors are being widely used as drive motors in audio, optical, office and other various types of equipment.
FIG. 3(A) is a partially cut-away side elevation of an example of a miniature motor, and FIG. 3(B) is a diagram of assistance in explaining the state where brushes are supported by a motor case cover plate in a miniature motor.
In FIG. 3(A) and (B), reference numeral 1' refers to a brush arm; 2' to a brush based end or brush base; 3' to a terminal; 4' to a motor case; 5' to a motor case cover plate; 6' to a bearing; 7' to a brush receiving recess or hole; 8' to a rotor; 9' to a commutator; 10' to a magnet; 11' to a shaft; and 12' to a shaft hole, respectively.
As shown in FIG. 3(A), the shaft 11' to which the rotor 8' and the commutator 9' are fixedly fitted is rotatably supported by the bearings 6' provided on the motor case 4' and the motor case cover plate 5', and housed in the motor case 4' having therein the magnet 10'. The brush arm or brush motor arm 1' for making electrical contact with the commutator 9' is fixedly fitted onto the motor case cover plate 5' in such a manner that the brush base or brush base end 2' is inserted into and engaged with the brush hole 7' provided on the motor case cover plate 5', as shown in FIG. 3(B).
The brush arm 1' fitted in the aformentioned state, when making sliding contact with the commutator 9', tends to cause chattering due to the vibration caused by irregular surfaces of commutator segments, leading to unwanted phenomenon, such as lowered commutating performance. To prevent such unwanted phenomena, it has heretofore been practiced that a rubber plate or film is applied to the brush arm 1' as a vibration-damping means with rubber or acrylic adhesive.
FIG. 2(A) is a front view of a vibration-damping device of the conventional type in which a rubber plate is applied to the brush arm, and FIG. 2(B) is a side elevation of the same.
In the figures, reference numeral 1' refers to a brush arm; 13' to a rubber plate, 14' to a prong of the brush arm 1', respectively.
When a vibration-damping rubber plate 13' is applied to the fork-shaped brush arm 1', the rubber plate 13' adheres to all of the prongs 14' of the brush arm 1, decreasing the resiliency of each prong 14'. This makes it difficult to allow independent movement of each of the prongs 14'. This results in a loss of the intimate contact of the fork-shaped brush arm 1' with the commutator, and accordingly to a loss of the spark-quenching effect that would otherwise be improved by the multi-point contact of the brush arm 1' with the commutator. Furthermore, the conventional vibration-damping means involves an additional process of applying the rubber plate 13' to the brush arm 1'.